Fibrinopeptide B is the 14-amino acid peptide that thrombin releases from the N-terminus of each B-beta chain of human fibrinogen. Cleavage exposes the B knob on the remaining fibrin molecule, allowing a fibrin knob-hole interaction. Each fibrinogen molecule contains two B-beta chains and can therefore release two copies of Fibrinopeptide B.[ref]
Fibrinopeptides A and B release in the process of surface fibrin formation by Tomas Riedel and others. Introduction: twofold chain composition, 14-residue peptide and B-knob exposure
Its release need not track Fibrinopeptide A release identically. A study comparing dissolved and surface-adsorbed fibrinogen incubated the preparations with thrombin and measured the released peptides by high-performance liquid chromatography. Surface-bound preparations released Fibrinopeptide B without the characteristic solution-phase lag; densely adsorbed preparations could release more Fibrinopeptide B than Fibrinopeptide A.[ref]
Fibrinopeptides A and B release in the process of surface fibrin formation by Tomas Riedel and others. Methods: polystyrene wells and HPLC; Abstract and Figures4–5: altered lag and release proportions
The experiment shows why a measured fibrinopeptide ratio needs its reaction conditions. Molecular presentation at a surface changes access to cleavage sites, so a typical sequence observed in solution should not be turned into an unconditional rule for every preparation.
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